Want to know a secret? Young chemists may dismiss the idea of needing to test for the presence of water after a chemical reaction,  but when you tell them they can create invisible ink in the process, that might get their attention! The third part in a series of ten short videos discusses two simple tests that can indicate water has formed by hydrating anhydrous solids.

Concepts

water, hydration, making observations, indicators, solids and liquids

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Additional Tags

science

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Instructional Ideas

• Provide an article about the uses of invisible ink throughout history; follow up by having students make their own cobalt (II) chloride solution and try their hand at secret messages
• Ask the class to show the differences between an anhydrous substance and one that is hydrated by looking at their chemical formulas

Classroom Considerations

• Turn subtitles on to assist with note-taking

Pros

• Video includes the interesting, real-world application of cobalt (II) chloride as invisible ink and as an indicator of water's presence
• Can be used as a stand-alone resource or shown as a continuation of the second video in the series, which also shows chemical tests

Cons

• None